Project summary: Palpation remains one of the simplest yet effective methods for detecting malignant breast lesions because the stiffness of breast tumors usually differs significantly from surrounding tissues. Mammography has been the main tool of breast imaging for many years, mostly to detect microcalcifications (MCs) which can be associated with breast malignancies. However, this method has limited sensitivity, especially in dense breasts. Conventional B-mode ultrasound (US) imaging has been increasingly used for breast imaging. However, this method is not sensitive to tissue stiffness. Besides, US imaging suffers from speckle artifact that masks small structures; thus, it is difficult to detect MCs, and in some cases, masses are hard to detect in this method. Significant effort has been invested to develop improved breast imaging techniques, especially those that provide palpation-like information. Vibro-acoustography (VA) is a novel non-invasive imaging method that produces such information. Since VA uses a new and unique intrinsic characteristic of tissue, it needs to be fully investigated to compare its capabilities to the more traditional breast imaging techniques. Using an experimental VA system, we have demonstrated the capability of this method to image breast in vivo, detect malignant and benign lesions, and identify MCs. In light of these results, the next logical step is to evaluate the feasibility of implementing a clinical breast VA imaging system. The existing experimental system uses a transducer housed in a water tank and electromechanical scanning technique. Using an array transducer is an important step in translating VA from experimental stage to clinical applications employing modern electronic scanning with hand-held probe. The purpose of this research is to investigate a VA system based on an array transducer for breast imaging. Here, we study breast imaging with linear array and evaluate its performance in detection of lesions in human breast. We will also investigate the feasibility of using a cutting-edge-technology 2D reconfigurable array with full 2D focusing and steering capability for breast VA. Such a system would have superior resolution and scanning speed desired for clinical 3D VA. The goals of this research will be achieved in 3 specific Aims: (1) Develop a VA system with a linear-array transducer for breast imaging; (2) Test the performance of the new VA system in humans; (3) Evaluate the 2D reconfigurable arrays for breast VA. Successful completion of this research will open the way for a new class of breast imaging tools. VA images are related to tissue stiffness, which is an important marker of malignancies. The combination of features offered by VA, such as sensitivity to stiffness, lack of speckle in image, and sensitivity to MCs, would have a significant impact in breast cancer detection. Relevance: This research aims at developing a new breast imaging tool. We examine the effectiveness of this new method as a diagnostic tool in detection of breast lesions and breast cancer. [unreadable] [unreadable] [unreadable]